BIM [1]} is a refined, iterative method of FGSM that generates an adversarial signal. At each iteration, BIM will take a small step \(\alpha \)  and clip the result using \({\varepsilon }\) :
\(\mathbf {x}^*_{n+1} = clip_{\operatornamewithlimits{\mathbf {x}},{\varepsilon }}\left(\mathbf {x}_n^*+\alpha \cdot sign\left(\nabla _{\operatornamewithlimits{\mathbf {x}}} J\left(\theta ,{\mathbf {x}^*_n},y\right)\right)\right),\) 
